Frankie, the shy Brooklyn teenager at the center of Eliza Hittman’s “Beach Rats,” has a soft, low voice, a well-muscled physique and intense blue eyes that seem to contain worlds of private heartache.

During the course of the movie, more than a few strangers will stare longingly at that physique and into those eyes, most of them middle-aged men whom Frankie meets in online chat rooms at night, seeking a flash of skin, a physical encounter or just a sweet, fleeting moment of intimacy.

The viewer spends a fair amount of time studying Frankie as well, and although it would hardly be accurate to describe the movie’s gaze as innocent — Hittman’s camera is acutely and unapologetically magnetized by the sensual beauty of young people — it is guided less by any prurient impulse than by a determination to peer clearly and sympathetically into a young man’s conflicted soul.

And Harris Dickinson, the spellbinding British newcomer who plays Frankie, rewards the director’s scrutiny with piercing emotional depth and a startling lack of self-consciousness.

The marvel of his performance, and of this sweatily evocative coming-of-age drama, stems from a willingness to leave a great deal unstated.

She follows Frankie and his buddies as they roam Brooklyn’s beaches and boardwalks, picking pockets, smoking weed and killing time.

The specter of “Beau Travail” (2000), Claire Denis’ humid, intoxicating ode to the beauty of men at work, seems to loom over this movie’s grainy, tactile 16-millimeter images (filmed by the French cinematographer Helene Louvart). Shots of bare legs and shirtless torsos are assembled into a feverish aesthetic of desire.

Images and textures speak far more meaningfully than words here — and a good thing, too, considering how little Frankie has to say for himself. He’s 19 and out of school, with no job prospects or dreams.

At home he sits around watching his father (Neal Huff) waste away in the final stages of terminal cancer, while dodging questions and other attempts at small talk from his stressed-out mother (Kate Hodge) and younger sister (Nicole Flyus).

Eventually, he starts half-heartedly dating a girl named Simone (a terrifically sharp Madeline Weinstein), who warily warms to the sweet, sensitive side that Frankie occasionally allows to peek out.

“I don’t really know what I like,” Frankie tells an online admirer, although his first few hook-ups give the lie to that statement, as does the blissful sense of erotic release that emanates from each encounter.

Later Frankie will tell another prospect that “I don’t really think of myself as gay,” and although the movie might know better, it’s also sensitive enough not to foist any labels or judgments on someone trying, both honestly and dishonestly, to figure out who he is.

If the film is mainly about Frankie’s confusion, it’s also a potent evocation of his particular time and place. The poignancy of his struggle is heightened by the movie’s timeless and idyllic Coney Island imagery, as Frankie finds occasional distraction in the sight of fireworks exploding overhead, or the pleasure of a few minutes spent splashing in the surf.

“Beach Rats” understands how the most inconvenient feelings can conceal themselves in broad daylight, and like “Beau Travail,” it acknowledges the perilously thin line between performative machismo and repressed desire.

The film is so skilled at telling its story through visual detail and atmosphere that you can sense the gears shifting in the second half, when Frankie tries to open up to his friends — a tentative attempt to reconcile the two sides of his double life that spirals recklessly out of control.

It’s a shocking yet curiously inevitable turn of events, and Hittman neither soft-pedals nor exaggerates the consequences. To the end she simply keeps on looking, with a gaze as compassionate as it is unsparing, at a young man who turns out to be far more than meets the eye.